The Difference between Pipes and Tubes

Pipe and tube are same in shape etc. But only difference is the pipe is used for Transferring Material (Gas, Liquid etc.)

And where it is used for Heat Exchanging purpose , It is called tube.

Pipe is identified by NB and thickness is defined by Schedule whereas Tube is identified by OD.

Pipes
A pipe is measured ID
A pipe is measured ID

The purpose with a pipe is the transport of a fluid like water, oil or similar, and the most import property is the capacity or the inside diameter.
For a ASTM A106 Seamless Pipe, ASME SA106 pipe the inside diameter –

Wall Thickness beyond XXH, including:
– Up to 4inch wall in 20inch through 24inch OD
– Up to 3inch wall in 10inch through 18inch OD
– Up to 2inch wall in 4inch through 8inch OD

The inside diameters are close to 2″ and the nominal diameter related to the inside diameter. Outside diameter are 2.375″ for both schedules.

Since the outside diameter of a single nominal pipe size is kept constant the inside diameter of a pipe will depend on the “schedule” or the thickness of the pipe. The schedule and the actual thickness of a pipe varies with the size of the pipe.

It is common to identify pipes in inches by using NPS or “Nominal Pipe Size”. The metric equivalent is called DN or “diametre nominel”. The metric designations conform to International Standards Organization (ISO) usage and apply to all plumbing, natural gas, heating oil, and miscellaneous piping used in buildings. The use of NPS does not conform to American Standard pipe designations where the term NPS means “National Pipe Thread Straight”.

Nominal Bore (NB) may be specified under British standards classifications along with schedule (wall thickness).

The tolerances are looser to pipes compared with tubes and they are often less expensive to produce.

Tubes
A tube is measured OD
A tube is measured OD

The nominal dimensions of tubes are based on the outside diameter. If we look at the outside diameter of a 2″ pipe is 2.125″, relatively close to 2″.
The inside diameter of a tube will depend on the thickness of the tube. The thickness is often specified as a . If we look at the wall thickness of 0.083″of a 2″ pipe is gauge 14.

The tolerances are higher with tubes compared to pipes and tubes are often more expensive to produce than pipes.

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